Two rare {M(2)(MoO(4))(2)}(n) chain-containing molybdate-based metal–organic complexes with a bis-pyrazole-bis-amide ligand: fluorescent sensing and photocatalysis performance

By introducing a bis-pyrazole-bis-amide ligand, N,N′-bis(1H-pyrazole-4-carboxamide)-1,4-benzene (L), two molybdate-based metal–organic complexes containing {M(2)(MoO(4))(2)}(n) (M = Co, Zn), [Co(2)L(2)(MoO(4))(2)]·H(2)O (1), [Zn(2)L(2)(MoO(4))(2)]·H(2)O (2), have been prepared under hydrothermal/solvothermal conditions. X-ray diffraction analyses reveal that both 1 and 2 are isostructural. An interesting structural feature is that a kind of {M(2)(MoO(4))(2)}(n) chain could be found in 1 and 2, although different raw materials [Mo(7)O(24)](6−) and [PMo(12)O(40)](3−) anions were utilized. Then these chains are further linked by L ligands into a two dimensional (2D) structure. The title complexes represent the first examples containing {MoO(4)} units and pyrazole-/or amide-derivative ligands. Complexes 1 and 2 exhibit distinct performances due to different metal centers, with 2 acting as a fluorescent sensor for Fe(3+), MnO(4)(−), CrO(4)(2−) and Cr(2)O(7)(2−), but 1 being a better photocatalyst towards degradation of cationic dyes methylene blue (MB) and neutral red (NR).